Effect of magnetic-field heat treatment on directional growth of magnetite in glass ceramics

Abstract

The CaO–MgO–Al2O3–SiO2 slag glass ceramic system was prepared by traditional melting, using solid Baiyun Obo tailings waste as the main raw material. The effects of mass fraction of Fe2O3, added in the range of 0%–15%, on the crystallization mechanism and microstructure of this ceramic were studied by means of differential scanning calorimetry, x-ray diffraction, scanning electron microscopy, and electron back-scatter diffraction phase identification. It was verified that Fe ions can destroy the glass network structure in these glass ceramics to promote crystallization. The production of Fe3O4 magnetite in a second phase and the gradual increase in Fe3O4 magnetite content was caused by an increase in the Fe2O3 content added in the glass ceramic. The results showed that the magnetite phase grew in the form of dendrites, which was promoted by magnetic heat treatment when compared with conventional heat treatment in a muffle furnace. According to results of the electron back-scatter diffraction analysis, the magnetite dendrite formation process took precedence over formation of the silk texture of the {1 1 1} crystal family.